Redundancy in Innate Immune Pathways That Promote CD8⁺ T-Cell Responses in AAV1 Muscle Gene Transfer.

Area of Science:

• Immunology
• Gene Therapy
• Molecular Biology

Background:

• Adeno-associated viral (AAV) vectors are crucial for in vivo gene therapy.
• Immune responses, particularly CD8+ T-cell activation, limit AAV efficacy.
• Innate immune sensing pathways contribute to T-cell responses against AAV-transduced cells.

Purpose of the Study:

• To identify innate and cytokine signaling pathways driving CD8+ T-cell responses to AAV1 vectors in murine skeletal muscle.
• To determine the necessity of blocking these pathways for effective gene transfer.

Main Methods:

• Administration of AAV1 vectors to murine skeletal muscle.
• Genetic (e.g., MyD88, IL-1R1 deficiency) and antibody-mediated blockade of innate immune pathways (TLR9, IL-1R, dsRNA sensing).
• Vector engineering strategies including CpG depletion and inhibitory sequences, combined with muscle-specific promoters.

Main Results:

• Blocking single innate pathways reduced CD8+ T-cell responses at low AAV doses but was ineffective at high doses.
• Simultaneous blockade of at least two pathways (IL-1R1/MyD88 and TLR9/Type I IFN) was required for efficacy at higher doses.
• CpG-depleted, TLR9-inhibited AAV vectors with muscle-specific promoters sustained transgene expression with minimal T-cell response.

Conclusions:

• Redundancy of innate immune pathways necessitates multi-pronged blockade strategies for effective AAV gene therapy.
• Innate immune evasion/blockade alone may be insufficient due to pathway overlap.
• Optimized vector design and promoter choice are critical for sustained transgene expression and immune tolerance.